It is well known that, if a sudden demand for increased torque is received by a diesel engine, a large amount of soot will be produced by the engine due to mis-fuelling of the engine. That is to say, to meet the requested torque demand a specific amount of fuel is required but the amount of ingested air is initially lower than that required to efficiently combust this volume of fuel due to the low initial speed of the engine. The result of this mis-fuelling is the production of soot from the engine due to the inefficient and incomplete combustion that takes place.
This mis-fuelling is disadvantageous in several respects. Firstly, fuel is wasted and therefore the fuel economy of the engine is reduced, secondly, unnecessary emissions are produced including the above referred to soot, thirdly, over fuelling produces un-burnt fuel in the engine which is absorbed into the lubricating oil, and fourthly, the soot produced rapidly fills any particulate filter provided to remove the soot from the exhaust gasses of the engine.
One approach to this problem includes restricting the amount of soot that is produced during such a transient event by modifying the target torque to be provided by the engine. However, a relatively high level of soot is still produced because an overall objective is to minimize the loss of potential torque output obtainable from the engine. A large amount of fuel or soot in the oil will reduce the lubricating properties of the oil. Furthermore, if the amount of fuel in the oil becomes very high, this high level of fuel in the oil can lead to engine runaway if the highly combustible fuel/oil mix is ingested back into the engine via an engine breather system.
The soot loading of a diesel particulate filter (DPF) affects the efficient operation of a diesel engine because as the DPF fills with soot the back pressure on the engine increases and so the torque output attainable from the engine will tend to drop. Therefore, a DPF may be regularly regenerated by burning off the soot stored in it. To do this, fuel is injected into the engine late in the combustion cycle so that un-burnt fuel travels towards the DPF where it auto-ignites in an upstream catalyst before entering the DPF and the exhaust gases at an increased temperature enter the DPF and burn off the soot. However, this process has two main disadvantages. Firstly, fuel is wasted regenerating the DPF, and secondly, the late injection of the fuel often result in un-burnt fuel impinging against the cylinder wall of the engine where it is readily absorbed into the oil thereby increasing the amount of fuel in the oil.
The inventors have recognized the issues with the above approaches and offer a method to at least partly address them. In one embodiment, there is provided a method for controlling an engine system having a diesel engine, at least one emission control device and oil to lubricate the engine, the method comprising adaptively varying an operation of the engine to reduce the production of soot by the engine based upon at least one of the current state of the emission control device and the current state of the oil of the engine.
In this way, the soot production of a diesel engine is adaptively reduced so as to increase the time periods between DPF regeneration events, thereby reducing the amount of fuel used during the life of the diesel engine for these events. The present disclosure may offer several advantages. For example, decreased fuel consumption in DPF regeneration may result in enhanced fuel economy and decreased soot production may result in decreased emissions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.